The outer radius should remain constant, as should the absorption (but
see [1]}) so we constrain these by simultaneously
fitting three datasets from various points in the outburst with the
modified diskir model, together with X-ray absorption
parameterised by wabs and UV reddening by redden. Assuming
standard gas to dust ratios allows us to tie \(E(B-V)=1.5 \times N_H/10^{22}\)  (GDP08). This gives a best fit at \(N_{H}=2.1\times 10^{21} cm^{-2}\)  and \(R_{out}=10^{5.25}R_{g}\) , which are fixed to
these values in all fits hereafter.
